code: def test_generate_mixes_using_all_examples_plus_random_examples(self):
      sourceid_to_exids = [("source1", i) for i in range(100)] + [
          ("source2", i) for i in range(100)
      ]
      exid_to_mixids = create_dataset_lib.generate_mixes(
          val="unused",
          num_mixes=200,
          sourceid_to_exids=sourceid_to_exids,
      )
      self.assertEqual(set(range(100)), exid_to_mixids.keys())
  
file_path: magenta/magenta/models/onsets_frames_transcription/create_dataset_lib_test.py
imports: import itertools
  from magenta.models.onsets_frames_transcription import create_dataset_lib
  import numpy
  import tensorflow.compat.v1
label_desc: Use image node_id 5 for calling the CreateDatasetLibTest obj's underlying member method code with example usage: obj.test_generate_mixes_using_all_examples_plus_random_examples() without return types